GenRad traces its origins back to 1906, when Melville Eastham co-founded the Clapp, Eddy and Eastham Company. Located in Boston, the company was established to manufacture x-ray machines. In 1907 the company was renamed the Clapp-Eastham Company. The company began to manufacture heavy-current keys, tuning coils, spark gaps, crystal detectors, and many other components used by professional radio and ham radio operators ("hams"). In 1910 Clapp sold his portion of the business to O. Kerro Luscomb. By that time the company was a staple of the radio industry; its customers included such radio pioneers as E. H. Armstrong, K. A. Fessenden, John Hays Hammond Jr., G. W. Pickard, G. W. Pierce, and John Stone.

Eastham recognized an emerging need for instrumentation in the developing radio field. In 1915 he withdrew from active participation in Clapp-Eastham and founded the General Radio Company. Eastham immediately began designing new instruments and landed a commission to build a nine-phase, synchronous, commutator-type rectifier for the American Telephone and Telegraph Company (AT&T). This rectifier played a part in the early history of the radio-telephone. In 1915 AT&T had successfully made the first transcontinental telephone call via landlines. AT&T and its business partner, Bureau de Postes, Telegraphes et Telephones in France, was worried that World War I would interrupt communications between the two continents and wanted to see if radio could be utilized to extend telephone communications across the Atlantic. The Bureau des Postes installed a receiver on the Eiffel Tower; AT&T erected a transmitter in Arlington, Virginia, using 500 fifteen-watt vacuum tubes connected in parallel, and General Radio's synchronous rectifier supplied the high voltage required. It would still be many years before a practical, reliable transatlantic telephone would arrive.

General Radio continued research and development, and in 1916 it published its first instrument catalog. Besides AT&T, other early customers included the General Electric Company and the National Bureau of Standards. When the United States entered World War I, General Radio got caught up in the national effort and found demand for its product increasing. The company began manufacturing large amounts of portable wave meters and crystal sets for trench-warfare communications. At this time, another General Radio part played a small role in another historic radio event. Some of the first instruments shipped for use in the war were a number of precision air capacitors, or "condensers." The capacitor was used in an Army laboratory to tune the first super-heterodyne receiver. Today, the same super-heterodyne circuit is used in virtually every television, radar, and communication receiver worldwide.

After World War I there were still almost no receivers except those built by radio hams. The home-built receiver craze developed practically overnight as everyone decided that they could do it, too. General Radio, which had been supplying hams with high-quality components for years, now found itself swamped with tens of thousands of orders. The demand persisted for approximately three years, when complete sets became available at reasonable prices, and the do-it-yourself fad died as quickly as it was born. In 1921 the company contracted with the U.S. Navy to manufacture hydrophones, which were used to detect underwater sounds. In 1924 General Radio launched into the measurement business in earnest and began developing and commercializing its long line of instruments. By 1932 the company was shipping products all over the world, and by 1937 General Radio's exports reached 39 percent of total sales.

The company had pioneered the cathode ray oscilloscope during the 1920s. As satisfactory American tubes reached the market, and demand for oscilloscopes developed, lower-priced competition appeared. Believing that oscilloscopes could be better supplied by others, the company dropped out of the business. In the 1930s new techniques underlying television and radar rekindled interest, and in 1938 the company developed a wide-band oscilloscope. The instrument was ahead of its time and was never produced because it was deemed too expensive and complicated.

The company entered World War II with two products that played important parts in the war effort— the "Variac" continuously adjustable autotransformer and the "Strobotac" short-flash light source. The Variac was used to efficiently control electrical power; the Strobotac was the progenitor of electronic-flash units used by photographers and makes possible the observation, in slow motion, of cyclically recurring events. The company was flooded with orders when the industrial mobilization of World War II started. During the war, General Radio won five Army-Navy "E" awards for excellence in the production of war materials.

As electronics companies went public in the stock market surge of the 1950s and 1960s, General Radio continued to quietly expand its ownership among its own employees. The company went public in 1978. It performed well through the 1980s as a tester of PCBs but ran into trouble during the 1970s when it entered the chip side of the testing market. By 1980 the need for electronic-equipment testing and, in particular, for greater productivity through automatic testing had been increasing because of the rapid development of electronic semiconductor device technology, the development of many new and diverse applications of electronic technology, and the shortage of electronic engineers and technicians. At that time, GenRad offered products in two general product categories: electronic-manufacturing test and design; and vibration analysis and acoustics.

As a result of its acquisition of Futuredata Computer Corporation in 1979, the company offered a line of microprocessor-development systems that assisted in the development of microprocessor-based products by simulating the operation of the microprocessor. In January 1980 the company completed formation of GenRad Semiconductor Test, Inc., as an 80 percent owned subsidiary to develop and manufacture systems to be used by producers of electronic semiconductor devices in manufacturing test applications. GenRad's management believed that the ability to provide an integrated line of circuit and component test equipment across a broad spectrum of applications had become an important competitive factor. Accordingly, the company had developed or acquired new entries for circuit design, incoming inspection, circuit testing, field service, and repair depot markets. GenRad's other product line, vibration analysis and acoustics products, was unprofitable until 1979, largely as a result of high marketing expenses and, in the case of digital-signal-processing systems, high manufacturing expenses as a result of over-reliance on purchased subsystems. In 1977 the company began new methods of marketing these products and redesigned its digital-signal-processing products.

In 1985 electronic equipment and semiconductor manufacturers experienced sales significantly lower than anticipated. As a result, they reduced their purchases of capital equipment, including automatic testing equipment. As a result of these and other factors, GenRad experienced a loss in its 1985 fiscal year of approximately $52 million. This weakness in demand continued into 1986; in the first quarter of the year the company experienced a loss of approximately $8.5 million.